1. Field of the Invention
The present invention relates to a hard coating film and a target used for forming the same. More particularly, the invention relates to a hard coating film formed on a substrate for enhancing the wear resistance thereof, and also relates to a target for forming the hard coating film, in the fabrication of cutting tools to be used for such purposes as metal cutting, drilling and end milling, metal dies to be used for such purposes as forging, press molding and extrusion molding, and jigs and tools to be used for such purposes as punching and blanking.
2. Description of the Related Art
Conventionally, on a cutting tool made of a substrate such as cemented carbide, cermet or high-speed tool steel, for example, a hard coating film formed of such a substance as TiN (nitride of Ti), TiCN (carbonitride of Ti), or TiAlN (complex nitride of Ti and Al) has been provided for enhancing the wear resistance thereof. In particular, as disclosed in Patent Document 1 indicated below, a hard coating film formed of TiAlN, which has higher wear resistance than TiN and TiCN, is suitable for cutting tools to be used for high-speed cutting operation or for cutting tools to be used for cutting high-hardness work materials such as quench-hardened steels. Further, as a hard coating film having enhanced wear resistance, there is disclosed a coating film formed of TiAlN containing Cr as an additive component, which provides a characteristic of improved oxidation resistance by increasing the content of Al while keeping a cubic crystal structure for ensuring high hardness (as disclosed in Patent Document 2). Still further, a hard coating film formed of TiCrAlN containing Si and B as additive components has been proposed for higher oxidation resistance (as disclosed in Patent Document 3), and a hard coating film formed of CrAlN containing Si, B, and at least one species selected from Nb, Mo, W, and Ta as additive components has been proposed for improvement in oxidation resistance (as disclosed in Patent Document 4). Furthermore, Patent Document 5 discloses a hard coating film having excellent wear resistance, which is formed of a nitride of a composition represented by the formula AlxTi1-x-y-zMyRz, (where M denotes at least one species selected from Si, Cr, W, and Mo; and R indicates at least one species selected from Y, Ce, La, and other rare earth metals including misch metals; and the following atomic ratio conditions are specified: 0.05≦x≦07, 0.02≦y≦0.25, and 0.0005≦z≦0.05). Moreover, for the purpose of ensuring wear resistance and other desirable characteristics, a hard coating film (TiSi)(NB) formed of TiN containing Si as an additive component, and a hard coating film (CrSi)(NB) formed of CrN containing Si as an additive component have been proposed (as disclosed in Patent Documents 6 and 7). Still further, a hard coating film (TiCr)(CNO) has been proposed (as disclosed in Patent Document 8).
Nevertheless, it has still been desired to provide an improved hard coating film having higher oxidation resistance and higher wear resistance in order to meet an increase in hardness of work materials and an increase in cutting speed required therefor in recent years.